dude, I don't have time to give you a whole step-by-step process. You can do your own research using the power of Google. Get an EIN or ITIN. There are also other issues like what type of registration (sole prop., partnership, corporations(S, R)) etc.
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I am not an immigration attorney nor do I have any experience litigating immigration cases. As always, seek professional advice before pursuing any course of action. I cannot be held accountable for any consequences of my comments.